Fissure detector for steel rails



May 5, 1931. E. A. SPERRY 1,804,330

FISSURE DETECTOR FOR STEEL RAILS Filed Aug. 27, 1927 4 Sheets-Sheet 1 '3 INVENTOR [177E]? 19.5PERRY y 1931. E. A. SPERRY 1,804,380

FISSURE DETECTOR FOR STEEL RAILS Filed Aug. 27 1927 4 Sheets-Sheet 2 IHH I I .1 llllllllli IIIIIIHIHIII INVENTOR fL/VERfiZSPEmPY A TORNEY.

E. A. SPERRY 1,804,380

FISSURE DETECTOR FOR STEEL RAILS May 5, 1931.

Filed Aug. 27, 1927 4 Sheets-Sheet I5 Y 86 ATTO R N EY May 5, 1931. E. A. SPERRY FISSURE DETECTOR FOR STEEL RAILS Filed Aug. 27, 1927 4 Sheets-Sheet 4 llll' llll-i f. 1 m mlmlm Ill P- L- INVENTOR. fZ/VER/ZQPE/PPY I I I I I I I I l I I I I I I I I I 1 n I Patented May 5, 1931 UNITED STATES PATENT OFFICE ELMER .Al SPERRY, OF BROOKLYN, NEW YORK, ASSIGNOB, BY MESNE ASSIGNMENTS, TO

SPERIRY PRODUCTS, INC., F BROOKLYN, NEW YORK, A CORPORATION OF NEW YORK FISSURE DETECTOR FOR STEEL RAILS This invention relates to automatic means for detecting flaws or hidden fissures in metal bars, rails and the like and has es ecial applicationto the detection of such aws in rail- I '5 way rails either before or after they have been laid in the track. It is now thought that such flaws in very small form as shatter cracks are occasionally present in the rail as I it comes from the rolling mill and that the passage of the trains and heavy locomotives gradually increases the size of the fissure or flaw until the rail actually breaks, which, of course, on mainline tracks results in a derailment and many times in a serious wreck. The purpose of the present invention is to devise a testing apparatus for rails of such sensitivity and selectiveness that it will detect and indicate or record the fissure before it has reached a dangerous size and will not be afi'ected by or indicate (at least in a manner to be confused with the flaw indications) variations in the voltage supply or current flowing through the rail or poor contact of either the main or detector brushes with the rail.

According to this invention the testin apparatus consists essentially of means for passing a heavy'electric current through the rail orthe particular portion under test and providing means contacting with the rail head for detecting minute variations in the voltage drop in the railzhead as the apparatus and rail'are moved relatively, together with a highly sensitive means for amplifying the variations thus obtained and operating therefrom a recording device or indicator. Such amplifyin means preferably takes the form of a casca e system of thermionic tubes arranged to operate a relay for controlling or operating an indicator such as a recording pen on a chart,-a defect rail marker to mark a bad rail atthe flaw, .a signal or the like. The detector and amplifier are constructed in such a manner that variations in the supply voltage or current supplied to the rail does not make an indication which could be confused with the flaw indication. This may be accomplished either by constructing the a paratus so that no'indication at all is recor ed by such causes or so that a difi'erent 215,980, and in Great Britain July 22, 1927.

character of indication is made from such causes as compared to the indication caused by the flaw.

In the first mentioned case, three'or more detecting brushes are employed ineach group in combination with a balanced transformer or balanced resistances, so, that when a'variation in the main current flowing occurs, equal and opposite efi'ects are produced simultaneously between the first and second brushes and the second and third brushes, resulting in no indication being transmitted. In the caseof a flaw, however, a dissimultaneous variation is produced in the circuit as it passes successively between the first and] second brushes and between the second and third brushes, resulting in twov indications being transmitted. In the second case, a plurality of pairs of detector brushes are em-' ployed with a plurality of recording pens on a traveling chart, the pens being so arranged that when-a flaw is encountered successive marks are made on the paper in a predetermined arrangement, suchas strai ht across the chart, while for variations in t e current supply, due to any cause, the indications are staggered or in diflerent relative'positions than for the flaw.

In case my invention is employed for detecting flaws in laid track, I prefer to employ a testcar which itself supplies a heavy current to the track b vheavy brushes positioned on each side 0 and preferably close to the detector brushesQ If it is desired to prevent the car from interfering with the block signalling system an additional pair of brushes can be provided on the outside of the current supply brushes and connected by a heavy copper conductor. Where my invention is employed on rails before being laid, the rails may be mounted on a carriage and automatic means provided operated from the flawdetector for rejecting or separiage.

When used on laid track, the rail joints 1! rating out detectiverails which may comi also will be indicated so that it is desirable to distinguish between the rail joints and the flaws. Since the voltage drop variation 18 very much greater for a rail joint than for a flaw, the. size of the rail joint indicamarking device very sensitive one and a less sensitive one,

and for a rail joint, the least sensitive relay as well as'the two more sensitive ones.

This application is a continuation of my co-pendin application Serial No. 681,718 detector for rails, filed December 20, 1923.

1 Referring to the drawings in which several forms of the invention are shown:

Fig. 1 is a diagrammatic plan view of a rail test car adapted to be moved over the track after the rails are laid and having my invention embodied therein. I

Fig. 2 is a side elevation of the same.

Fig. 3 is a wiring diagram showing one form of a detecting and amplifying circuit for actuating the relay indicator.

Fig. dis a plan view of the recording pen adaptedlto be employed with the form of the invention shown in Figs. 9 to 11 and 17.

Fig. 4-a is a side elevation ofthe same.

Fi I 5 is-a wiring diagram showing a modified orm of detecting circuit but using the same arrangement of brushes as Fig. 3.

Fig. 6 is a diagrammatic view showing how my apparatus may be used to test rails in the steel mill before laid in the track.

Fig. 7 is a detail of said apparatus showing a trip for separating out defective rails.

Fig. 8 is a detail of a. portion of Fig. 7 showmg a clamp for introducing current into the rails. j i

Fig. 9 is a wiring diagram of a modified form of the invention employing contact brushes in pairs and an A.- G. amplifying system.

, Fig. 10 shows a D. C. amplifying circuit with a similar contact system to Fig. 9.

Fi 11 shows another form of A. G. amplifymg system.

Fig. 12 shows in diagrammatic form how my invention may actuate other forms of indicators besides recorders, comprising a rail marker, an audible signal, and a rail joint counter.

Fig. 13 is a side elevation of a form of nlilarlnng pen for recording the flaws on a c art. e

Fig. 14 is a plan view of the same showing the character of the chart record.

ig. 15 is a detail in section of the ink trough for the pens.

Fig. 16 is a vertical section of the rail Fig. 17 is a side view of a modified form of brush holder especially adapted for the form of circuit shown in Figs. 9 to 11.

Fig. 18 shows the character of indication made by this form of the invention.

For detecting flaws in laid track, I prefer to utilize a car 1 which itself contains means for supplying a heavy current to the rails.

Current is shown as supplied to each rail R and B through heavy brushes 2, 3, 4 and 5,

to which is connected a heavy current low voltage generator 6 which may be driven by a combustion or other engine 7 on the test car. Separate windingsfi' and 8 are. shown as provided for the two rails The fields-of both generators'may be excited by a separate .exciter 9 if desired. Between said heavy brushes I place one or more groups of detector or potentiometer brushes 11, 12- and 13 and 11', 12 and 13, which are designed to detect the slightest variation in voltage drop in'the railhead between the brushes of each group. These contacts may be of any suitable form such as small rollers, woven wire brushes or the like. The entire set of brushes,.both large and small, may be mounted on a common frame 14, which may be raised andlowered by any suitable means, such as abell crank lever 15 connected to the; frame by connecting link 16 and connected at its other end to an operating handle or lever 17 through link 18. Rail cleaning brushes 19 may also be provided to assure good contact with the rail. Said brushes may be revolved from the car axle 20 as by means of the gearing 21 there shown.-

on a Faraday transformer 24. As shown,

the brush 12 is connected to a neutral point between the two coils 22 and 23. The two coils are wound so that they are equal and opposite in their magnetic influence on the transformer ring 24. The secondary winding 25 on said ring is connected to. an amplifyingsystem (hereinafter described) for operatingthe recorder or indicator. In case between brushes 12 and 13, a change of current flow will be effected in the coils 22 and a fissure is passed over when said fissure is 23 in one direction, and as the fissure passes V under brushes 11 and 12 a change of current in the transformer windings will be efiected in the opposite direction so that a fissure will be indicated by two successiveimpulses. In

case, however, of variation in the current passing through the rail-due to any cause, such as a poor contact condition between the main brushes and the rail, jumping of the main brushes oil the rail, or any other cause, these two coils will act equally, oppositely and simultaneously on the transformer and, therefore, no indication will be produced.

The feeble indication produced by a flaw in the secondary winding 25 is amplified many times by placing the coil in electrical rela-v tion with a thermionic cascade amplifying system of the alternating current type in which the coil 25 is placed in circuit with the grid 26 of No. 1 tube. 27 1 Variations of the potential of the grid of this tube relative to the filament govern the other tubes of the amplifying system. Between each tube is shown a'suitable form of audio-transformer 28. The plate 29 of the last tube is in circuit with the relay coil 30 of the indicating or recording mechanism.

As shown, such mechanism is in the form of a recorder in which the said winding actuates a marker mechanism or pen 31 making an indication on the chart. when a flaw is encountered. The chart 32 (Fig. 1) is shown as continuously actuated from the car wheels as by means of bevel gearing 33 and a sprocket and chain 34. The chart, therefore, is ad-vanced'in exact proportion to the passage of the car over the track, so that the chart record is synchronized with thetrack and the location of a flaw may be scaled ofi' on the chart from the adjacent rail joint. Each pen or marker mechanism (Figs. 13- and 14) is shown as comprising a frame-Work 35 supporting an electro-magnet 36 and a spring arm 37 which carries at its free end a U-shaped pen 38, the inner end of which dips into an ink trough or well 39 (Figs. 13

I and 15). The pens may be mounted adjacent 7 one another with the magnets staggered, as

shown in Fig. 14 ment is produced.

The apparatus is further designed so that the rail oints, when passed over, make readily distinguishable indications 40 from the flaw indications 41 (Fig. 14) This not only avoids confusing the rail joints with the flaws but also enables the position of the flaw to be determined on the track by counting the rail so that a compact arrangejoints from a given point.

The several relays 30 or magnets 36 are, for this and other purposes, wound for different degrees of sensitivity. At least one magnet or relay 42, for instance, is relatively insensitive so that it is only actuated for rail joints, and in this instance is connected to both rails. All marks on center line 42' of the chart, therefore, indicaterail ointsg The other relays are preferably more sen.-

sitive, one half being connected to one rail andthe other half to the other rail, but their sensitivity may also be made different so plishing such results is suggested in Figs.6-

one relay would be actuated, for a-larger flaw two relays, and a serious flaw by all three marks. Thus the indications on the chart show at a glance the relative size of the fissure as well as its presence. Referring to Fig. 14, for instance, rail 'oints are shown at 40, because pen 42' is a justed only to be actuated by such, and a very small fissure in the left hand rail is shown at 43 because only the super-sensitive pen 46 is actuated by such a small flaw, and a larger flaw at 44 in the right rail and a very serious flaw at 45 in the le rail and at 41 in the right rail.

In Fig. 5 is shown a different flaw detect-' resistances for this purpose. In this systemthe three detector contact brushes 11", 12" and 13' are placed in circuit with a pair of variable resistances and 51 as shown, the tap 52 in resistance 50 being so adjusted that w en the potential drop through the rail head .is uniform then no current willfiow through the other resistance 51, since the voltage drop between brushes 11 and 12 equals that between 12" and 13". When, however, a flaw is assed over by brushes 11" and 12", the v0 tage drop increases resulting in a current flow in one direction through resistance 51 and when the flaw passes brushes 12" and 13", the current flow through resistance 51 is reversed. The lastnamed resistance is preferably connected through a 0 battery 52 to the grid of the first tube 53 of a D. C. cascade amplifying system. In this system I have shown separate C batteries 54 for the plate of each.

tube with a variable resistance 54 for adjusting the charge. I 7 7 Instead of moving the car along the track, it is obvious that the relative motion between the detector brushes and the rail may be produced by other means. For instance, if it is desired to testthe rail at the steel mill or at any time before it is placed in the track, apparatus such as shown in Fi 6 may be conveniently employed. Accor ing to this apparatus the rail R is run onto a carriage 60, and current is introduced thereto preferably by electro-magnetic clamps 61 and 62 gripped to each end of the rail head. The detector brushes 63'may then be caused to travel aloiig the rail head by any suitable means, such as by having themsupported 'in a carriage 64 rollin on overhead track-wa 65and moved as by eing linked to a trave 7 ling belt or chain 66 driven by any suitable power source (not shown).

If desired, automatic means may be proand 7 wherein 'the carriage supporting the rail is shown as hinged at one end and 'supimperfect rails from the perfect rails. As P the rail slides off the carriage and thus re- .lieve it of its weight, the springs 69 return the carriage to its normal position where it is again caught by the latch.

Another system'of introducing current-to therail is shown in Fig. 17. In this system four heavy brushes are employed, 73, 74, 75 and 76, the generator being connected to the two inside brushes and the outside brushes being cross-connected by-a heavy 0 .copper bar 77 of low resistance.- If the amplifying the variation in voltage drop be-. tween the members of .the pairs of contacts current then enters through brush 74 it will divide, half of the same flowing through the rail to brush 75, and the other half flow ing in the opposite direction through the rail to brush 73, thence through copper conductor 77 to brush 76 and thence back to brush 7 5, the spacingbetween brushes 74 and being equal to the combined distance between brushes 73 and 74 and brushes 75 and 76. By this means and by insulating the wheels on one side of the car from those on the other, leakage of current into the block signal system of the railroad and operation of the signals by the car is prevented, since the two outside brushes 75 and 76 prevent any current from leaking beyond the car. Besides, this enables one to tap the rail at. three points, i. e'., between brushes 73 and 74, 74and 7 5, and 75 and 76, with the employment of only one generator,'as shown by pairs of detector brushes 78, 79 and 80.' Between each pair 0 supply brushes as aforesaid',,I.p1ace apair o exploring or potentiometer contacts 78, 79 and 80 for very accurately detecting any variation in voltage drop in the small sections of the rail between the members ofeach pair of contacts.

Fi 10 represents .a preferred means for when a flaw is passed over. Said contacts are placed in; electrical relation w1th a cascade amplifying system 55 of the thermionic;

direct current type in which the contacts are placed so as to charge the grid 56 of No. 1 tu e 57 with a (say) negative potential, the variations in. the potential of the grid of this tube relative to thefilam'ent 58 govern ing the other tubes of the amplifying system. The more negative the grid potential be comes with respect to the filament,the lower the output of the amplifier.

plates If, however, no further means is employed,

case the brushes 78 bounce off, the rail,

thereby reducing the negative potential to zero. 'To correct this difficulty a resistance 82, on the order of 100,000 (more or less) ohms, is inserted across the brushes 78 and a variable potentiometer 83 is provided which may be adjusted to give a predetermined outut for the diflerence in potential drop due to the potentiometer and that due to the rail between the.brushes 78. If any flaw is encountered, the drop of potential at the rail increases and, therefore, the difference between the potential drop of the potentiometer and rail becomes smaller so that the output increases to actuate the indicator, but if the brushes bounce from the rail or bad contact is encountered, the drop at the rail becomes or approaches zero, and, therefore, the total potential increases and the output drops toward or to zero, resulting in an indication of a different character from that caused by a flaw.

Preferably also separate B batteries are provided for some or all of the tubes. If, for instance, the same B battery 84 were used for the last tube 85 as for the others any increase in flow of current therethrough would cause a drop in voltage of the B battery and, therefore, a drop .in voltage supplied to the of other tubes resulting in the rapid of an unstable condition. .With

buildin up n B battery 86 and 87 for the a separate other tubes,

this trouble is avoided. Eachunit of the amplifying system of all forms of the invention is preferably shielded as by metallic coverings 88, such covering also extending to the wires leading to the brushes 7'87980, as indicated at 89, so that outside electrical influences are carefully exf cluded. The last tube is connected directly 1? or indirectly to the electro-magnet 42' of-a recordingpen 46. (Figs. 4 and 12). Each pen or marker mechanism is shown as comprising a U-shaped magnet (Figs. 4 and 4-a), a magnetizing coil 121 which may have current continuouslysupplied thereto,

and said coil 42' in circuit with or controlled by the amplifying system."

An armature in the form of aspring plate 122 pinned at its base projects through said last-named coil and up between the endsof said U-shaped magnet, the armature being preferably of soft iron and ha g a pin 123 engaging a slot 124 in the reed 125 which holds the pen 46,. ping at one end 127 into an inkwell 128 and Said pen is shown as dipl 5 at the'other end 129 as hearing on the chart. T

As the win-ding '31 is excited the soft iron armature becomes polarized and is pulled towards one pole or the other of the permanent magnet as will be readily apparent, with a force proportional to the current flowing and against the spring bias of the plate 122, w

ich is represented in Fig. 12 by spring 130. As explained above, if a flaw is encountered, the pen will be pulled in one direction to cause mark 90, and if had contact is encountered or the potentiometer brushes bounce from the rail, the pens will be pulled in the opposite direction to cause marks 91, 91 and 91 as the current through coil 31' will then decrease instead of increase.

The pen will also be actuated at each rail joint as shown at 40', 4:0 and 40 but the rail joints will actuate the pens to a much greater extent than the flaws and also he more sharply defined, so that their markings may be readily distinguished from those caused by flaws on the chart. t will he understood that each set of brushes 78, 7 9 and 80 is connected to a separate amplifying-system and pen so that as shown there are three pens for each rail, each pen tracing a separate line on the chart and giving an indication 90, 90' and 90", of the flaw as the connected pair of brushes pass over the same. This not only gives a triple check on the flaw but also furnishes an additional means for distinguishing between a flaw and a case where the entire brush system 73, 74, and 7 6 bounces ed the rail, the case of non-contact with the rail, above considered, being .where the detecting brushes 78, 79 or 80 lose contact successively with the rail. The pens may be so arranged on the chart in staggered relation,

35.3.5 shown in Fig. 18, that for a flaw the markings 90, and 90" or 91, 91' and 91" on the chart appear in the same straight line across flaws,- but which-is elem by e effect causedby the rail joint. As

.the chart.

the same (Fig. 18). Where, however, the entire brush mechanism is bounced off the rail, the markings of the pen will be in staggered relation 92, 92- and 92", the three pens marking simultaneously but the markings appearing in staggered relation as the brushes are placed in staggered relation on In addition to or insteadof makings" record of the flaws, I may provide other Blind-- ave ling means. In Fig. 12, for instance, I shown both a. means for giving an audible :signal when a flaw is encountered and also a means for marking a defective rail at a point near the flaw. In this An extra conas norma y not to be closed b or moves in the opposite direction, "whencontact is lost or poor, said contact and also contact 98 (hereinafter described) are not closed under such conditions. ,1 When closed said contact excites a relay coil 94 which controls an q fmlture 91-having two sets of contacts MfsfldiM. The 11 per contact 94 is closed bygoxcititionqf sai coil! and is incircuit the pen mecha- 'rapidl cult.

lien with a. counter 96 or the like which counts the rail joints so that the defective rail ma be located by countin the number of 111' from a given point. gaid contacts 94, however, are normally maintained open by a spring 96' and dashpot 97. The back 0011- speaker and markingdevice will be operated because both the contacts 98 and 95 will be closed, since contact 93 is not closed, by reason of the insuficient movement of the pen. However, for rail joints, since contact 93 is closed, the loud-speaker will not be operated as when contact 93 is closed the back contacts at 95 will be open, and the contacts 94 through the counter 96 closed. For had contact conditions, also, no operation will occur as both contacts 93 and 98 remain open.

'As shown, the rail-marking device is in the form of a paint-daubing device (Fig. 16) Paint is placed in the container 100 to which is connected a source of compressed air through the pipe 100'. A valve 101 is placed be momentarily opened and a splotch of paint splashed on the rail, the valve being closed again by spring 104.

Other forms of am lification may obviously be used for amphfying the feeble-variations in voltage drop at the relay to actuate the indicator or signal. In Fig. 11 I have shown a transformer type of radio amplifier as distinguished from the non-inductive type,

such as shown in Fig. 10. According to this modification, a means is interposed for introducing a high frequency interruption of the primary circuit to render the use of the transormer type feasible.- Such an interrupter is indicated at 105 and comprises an arms.-

ture 106 normally biased to close back contacts 107 by means of the spring 108. A coil 109 in'circuit with switch 107 attracts the armature 106 to close contacts 110 which is in the'primary circuit. It will be understood that this contact device will vibrate to make and break the primary cirsaid circuit is placed a transformer 111, the seconds bein connected to the grid 112 of the tu 113. .From this point on an number of stages may beadded; as indicate by the transformer 114, and tube 115, the last tube having its plate 116 in cir coil: with the relsyjfilf as in the. de-

bad in Fi 10 .5 1; will be understood that in such a system the C battery 117 is adjusted to give a bias on the grid 118 of the last tube such that the relay only operates with a greater than normal variation due to the rail flaw or the like.

the grid of the detector tube 126, and also one side of the transformer 129, the other winding of which is connected to the plate of-the oscillator.

In passing, it should be observed that I prefer to position the pair of potentiometer contacts 79 between supply current brushes 74 and 75 closer to one brush than the other. This is because I have found that the heavy supply current spreads out to the web and base of the rail at 'more than a few inches away from its point of supply, so that a large part of it does not pass through the rail head, where the fissures occur. I, therefore, position the potentiometer contacts not more than a few inches away from a supply brush.

- Also, I prefer to employ means in the amplifier circuit (Fig. 10 such as condenser 120 shunted around resistance 121 to suppress oscillations of radio frequency so that only oscillations of much less frequency, such as occasioned by rail flaws, reach relay 31'.

It will be obvious that if desired a rail marking device, such as shown in Fig. 12,

may also be employed to mark every tenth rail or rail-joint (for instance) so thatafter the test car has passed over the defective rail may be readily located, even though the flaw itself is not marked. This may be accom plished by exciting solenoid 103 from a contact (not shown) on rail counter 96 or in any other suitable manner.

In accordance with the provisions of the patent statutes, I have herein described the principle and operation of my invention, together with the apparatus which I now consider to represent the best embodiment thereof, but I desire to have it understood that the apparatus shown is only illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combination and relations described, some of these may be altered and others omitted without interfering with the more general results out- .lined, and the invention extends to such use.

Two stages of transformer am- Having described my invention, what I claim and desired to secure by Letters Patent is: i

1. Apparatus for detecting flaws in metallic bars, rails or thelike comprising means movablerelatively to the rail for detecting minute variations in the flow of current from point-to point through the rail, means for amplifyin such variations to give an indication of the aw, and means for rendering separate indications for the rail joints.

' 2. In a flaw detector for metallic bars, rails or the like, means for passing acurrent through the bar being tested, means relatively movable along the bar for detecting variations in the voltage drop from point to point, and means for amplifying and recording such variations.

3. In a flaw detector for metallic bars, rails or .the like, means for passing a current through the bar being tested, means relatively movable along the rail for detecting variations in the voltage drop from point to point, means for ampli ing such variations, and means for difierentiatin between large and small variations where y large flaws may be distinguished from small flaws.

4. In a flaw detector for metallic bars, rails or the like, means for passing a current through the rail being tested, means relatively movable along the rail for detecting variations in the voltage dropfrom point to point, means for amplifying such variations, means for differentiating between large and small variations whereby the rail joints may 100 be distin ished from the flaws, and means for recor 'ng distinctively the flaws and rail joints.

5. The combination with a car, a traveling chart thereon, a plurality of recording 1 pens therefor, electrical contact means for measuring the rail-conductivity from point to point as the car moves along the rail, means for moving each pan successively as a point of high electrical resistance in the rail is passed over by the car, and means for moving said pens simultaneously as said contact means loses contact withthe rail.

6. The combination with a car, a traveling chart. thereon, a plurality of recording pens therefor, electrical contact means for measuring the rail conductivity from point to point as the car moves along the-rail, means for moving each pen as a point of high electrical resistance in the rail is passed over by 12 the car, andmeans for moving said pens in a different manner as said contact means loses contact with the rail.

7. A rail flaw detector comprising a plurality 6f spaced contacts adapted to be moved 12 along the rail, means for supplying a current to'the central'two of said contacts, a low resistance conductor between the outer two of said contacts, a pair of detector contacts between each adjacent pair of current-carry- 1 H tween any two of the contacts is the same as that between the other two contacts but in which a current flow is caused when a variation in said voltage drop occurs, and means for amplifying said how to cause an indication.

9. In a rail flaw detector,'the combination with means for supplying current to therail, of a plurality of contacts, means for moving the rails and contacts relatively to each other, a resistance circuit connected to said'contacts which is balanced as lon as the rail voltage drop between any two of t e 0011- V tacts is the same as that between the other two contacts but in which a current flow is caused when a variation in said voltage drop occurs, and means for amplifyingsaid flow to cause an indication.

10. In a rail flaw detector, the combination with means for supplying current to the rail, of a plurality of contacts, means for moving the rails and contacts relatively to each other,

a multi-winding transformer connected to said contacts in which no current E. MQF. is

generated in the secondary as long as the rail 5 rails or the like, means for voltage drop between any two of the contacts is the same as thatbetween the other two gcontac'ts, but in which an E. M. F. is caused when a variation in'said voltage drop occurs, and means for amplifying sald E. M. F. to cause an indication.

- 11. In a flaw detector for metallic bars, passing a current through the rail being tested, means movable relatively along the rail for detecting variations in the current flow atdifierent progressive points, means for amplifyin such varia-- f .tions, and means for progressive yrecording such amplified variations 12. In a flaw detector for metallic bars,

rails or the like, means for assing a current through the rail being teste means movable the r-Bio g frelatively along the rail fof detecting vane tions in-thevoltage .drop at 'difierehtprogressive points, meansforamplifying S variations and means for rogressively recording slich amplified variiltions and indis fi g ehu e magnitude; 1

13., In a detector cor,. ;a-havel1ing-chart' thereon, a Pfl fib'erefor, means on 'afi purrent-to the rail as thecir 66 on' or" in the current flow through the rail from point to point as the car passes therealong, means for amplifying such variations, and means actuated thereby for moving said pen.

14. In a detector car, a travelling chart thereon, a recording pen therefor, means on the car for supplying a current to the rail as the car passes therealong, electrical means on the car for detecting variations in the current fiow through the rail from point to oint as the car passes therealong, means for amplifying such variations, means actu ated thereby for moving said pen, and means for preventing like actuation of. the pen caused by Variations in the main current supply through the rail.

15.. In a flaw detector for metallic masses, means movable relatively to the mass for passing a current through the mass between spaced points, means movable relatively to the mass for detecting variations in the char 4 acteristics of current flow between said points, and means for preventing variations in the said current from affecting said detecting means.

1%. In a flaw detector for metallic masses, 7 7

means movable relatively to the mass for passing a current through the mass between -spaced points, means mechanically coupled to and moving with the said current passing means relatively to the mass for detecting .variations in the characteristics of current flow between said points, and means for preafiecting said detecting means. H g 17. In a flaw detector for metal bars, rails ;'or the like, contact means movable along the bar for'passinga current through the bar betweeni-spac ed points, means also movable with said first named means for detecting variations in the characteristics of current flow between said points, means for amplifying variations so detected, and means ac- };iuated thereby to indicate the location of aws.

venting variations in the saidicurrent from j :18. In a. flaw detector for metal bars, rails or the like, a source of electrical current,

means movable relative to the bar for intro-' ducin said current into the bar between spaced ints as said bar andmeansmove relativ y, a plurality of means for shunting a portion of the current passing between each pair of spaced means, and a common means for indicating variations in the current shunted throu h said second means 'for the purpose s iti ed. i

19. A aw detector comprisingfia car, a plurality of contacts on the car adapted to contact with the rail, means for passing through the rail between certain of said con tacts a current, certain other of said contacts being located between the first named contacts and adapted to furnish a shunt path C "for said current, a circuit actuated by variations in the current passing through second named contacts, and means for am- .pass over the rail, the spacing of the markers on the chart being such that the distincrality of spaced pens in a different tive mark of one marker for a given flaw or.

joint will lie in' line -,with the distinctive mark of the other marker for'the same flaw or joint.

' 21. In a rail flaw detector, a chart, a plumarkers for making duplicate records on the chart and a plurality of detector contactors adapted to successively.

pass over the rail, the spacing of the markers on, the chart being such that the distinctive mark of one marker for a given flaw or joint will bear a predetermined relationship on the chart to the. distinctive mark of the other marker for thesame flaw or joint.

22. In a detector car, a traveling chart thereon, a plurality of recording pens therefor, electrical contact means for measuring the rail conductivity from point to point, means for moving each pensuccessively as a point of high electrical resistance in the rail ispassed over by the car, ing said pens simultaneously as said contact means loses contact with the rail.

23. In a detector car, a traveling chart thereon, a plurality of recording pens therefor, electrical contact means for measuring the rail conductivity from point to point,

means for 'moving ,each pen as a point of high electrical resistance in the railis passed over by the car, and means for moving said manner as said contact means loses contact with the rail.

24;. In a flaw detector for metal bars, rails and the'like, means contacting with said bar and movable relative to the bar for passing a current through the barvbetween spaced points, and means also contactin with said bar' and movable-relative to the ar for detecting variations in the characteristics of current flow between said points.

25. In a flaw detector for metallic bars, rails and the like, means for passing a current between spaced points of said bar,- means movable relatively to said bar for detecting variations in the current flow from point to point, and flaw-indicating means actuated by said detecting means.

26. A rail flaw detector comprising a plurality of spaced contacts adapted to be moved along the rail, means for supplying a current thereto, a pair of contacts between said firstnamed contacts, means for detecting variations in the voltage drop therebetween, means for amplifying such variation, and means actuated thereby for furnishing an indication of sudden increases thereof;

- 27 A rail flaw detector comprising a pluand means'for movsignature.

along the rail, means for supplying a current to the central two of said contacts, a low resistance conductor between the outer two of said contacts, a pair of detector contacts between each adjacent pair of current-carrying contacts, means for detecting variations in voltage drop between the members of each detector pair, means for amplifying the variations detected by each, and means actuated thereby for furnishing aplurality of indications when sudden variations in voltage .drop

occur. 1

28. A rail flaw detector comprising a plurality of spaced contacts adapted to he moved along the rail, means for supplying a current to the central two of said'contacts, a low resistance conductor between the outer two of said contacts, a pair of detector contacts between each adjacent pair of currentchart, andrecording means therefor actuated by each of said amplifying means.

29. A rail flaw detector comprising a p rality of spaced brushes adapted to be moved- I along the rail, means for supplying electric current thereto, a pair of contacts between said brushes, means diiierently responsive to variations in the voltage drop due to flaws in the rail than those due to loss of electrical contact with said rail by said contacts, means for amplifying said different responses, and indicating means operated by said amplifying means.

In testimony whereof I have afixed'my ELME-B A. srEnRY. 

